Study On The Effect Of Magnetic Flocculation Treatment Of Landfill Leachate

The magnetic flocculation process was used as the pretreatment link of leachate ultrafiltration and nanofiltration membrane treatment system in Liucheng county landfill site,but the effect of magnetic flocculation treatment was inefficient,which leads to membrane blockage and fouling in subsequent membrane system.This problem is also a major problem in the field of leachate treatment at home and abroad.In view of this,the removal effect of magnetic flocculation of different water quality leachate in Liucheng and Guilin Shankou landfill was studied by magnetic flocculation orthogonal test and single factor test,and the influencing factors and optimization conditions were discussed.The particle size and morphology of magnetic sludge floc under different conditions were observed by laser particle size measuring instrument and optical microscope,and the mechanism of magnetic flocculation was discussed.In order to improve the effect of magnetic flocculation treatment of landfill leachate in Liucheng county and to provide theoretical basis for technological improvement,the main conclusions are as follows:（1）The order of influencing factors of magnetic flocculation treatment was:dosage of PAM>pH>dosage of PAM>dosage of magnetic powder.The results of orthogonal experiment show that Liucheng landfill leachate treatment of magnetic flocculation best test parameters were:PFSS dosage of 25 ml/L,pH 6.5,PAM dosage60 mg/L,powder dosage 600 mg/L when leachate COD concentration was 6570 mg/L,the removal rate reached 60.7%;When the concentration of COD TP and SS were1442 mg/L and 244 mg/L,respectively,the optimal parameters for magnetic flocculation treatment of landfill leachate in Guilin Shankou landfill were as follows:dosage of 20 ml/L PFSS 20 ml/L,pH 6.5%PAM 20 mg/L,magnetic powder dosage5.0 g/L,removal rate of COD TP and SS reached 71.09%99.13%and 97.54%,respectively.（2）The single factor test showed that adding enough PFSS was beneficial to the rapid release of CO₂ and separation of mud water from flocs,and to avoid the influence of bubbles on the separation of mud water in the later stage of flocs.pH affects hydrolysis of PFSS.In the range of pH 6.0⁸.5,the removal rate of COD and TP gradually decreased with the increase of pH,and pH affected the formation of bubbles and the flocculation effect of PAM.Adjusting the pH of flocculation environment to above 6.5 can effectively restrain the formation of subsequent bubbles and prevent the to sludge floatation in a short time.Addition of PAM can promote the aggregation of sludge floc and improve sludge settling performance.The addition of magnetic powder can promote the rapid settling of sludge floc.（3）In the process of magnetic flocculation,the particle size and form of sludge floc changed with the change of pH and magnetic powder dosage.When the dosage of PFSS increased from 15 ml/L to 21 ml/L,the average diameter of sludge gradually increased from 172.80μm to 194.29μm,and when the dosage of PFSS increased to31 ml/L,the average particle size of sludge gradually decreased to 159.20μm,the volume of flocs decreased,and the bubbles attached to the flocs became more and more obvious.When the flocculation structure became loose,the proportion of sludge particles with small diameter gradually decreased,and the proportion of large granular sludge gradually increased when the pH value of flocculation environment was6.0⁸.5,and the average particle size increased from 155.12μm to 286.22μm pH,which had little effect on the morphology of sludge floc.However,when pH is 6.0,there are obvious bubbles on the surface of sludge floc.When pH was adjusted to above 6.5,the bubble production could be effectively inhibited,and the average diameter of sludge increased from 114.53μm to 677.40μm when the dosage of PAM was 0⁴5 mg/L.When the dosage of PAM reached 20 mg/L,the average diameter of sludge particles was more than 500μm.At the same time,the volume of sludge floc increased,the less light transmission,the denser the flocs increased,the particle size of sludge floc increased with the increase of magnetic powder dosage,but when the dosage increased to 15 g/L,the average particle size of sludge tended to be stable.The more magnetic powder wrapped in the floc,the more close-grained,the greater the specific gravity.The experimental results show that the magnetic flocculation treatment process with PFSS can effectively reduce the concentration of COD and TP in landfill leachate and improve sludge settling performance.Moreover,it has the advantages of repeatable recycling,low construction cost,less equipment occupation and large treatment capacity,which can provide a new way for the pretreatment of landfill leachate.